The Township of Perth South is a lower-tier municipality in southwestern Ontario, Canada. It is in Perth County at the confluence of the Thames and Avon rivers. The township was created on January 1, 1998, from the amalgamation of the former Township of Blanshard and the former Township of Downie. The land area of Perth South is 393.14 square kilometers. The population in 2016 was 3,810. Canada's ninth Prime Minister, Arthur Meighen, was born in Anderson, a community in Perth South.